Drop impact phenomena have attracted the interests of scientists and engineers for more than one century, both because of their complex physical mechanisms and because they have a very large number of applications of practical relevance. Examples are inkjet printing, internal combustion engines, aerosol drug delivery, distribution of agrochemicals, and of course all spray applications, which are ubiquitous in industrial as well as in domestic processes, from painting or cleaning surfaces to spray cooling and firefighting. Whilst there exists a significant volume of literature about single drop impacts of simple (Newtonian) fluids, the number of works about fluids with complex microstructure (polymer melts or solutions, gels, pastes, foams and emulsions, etc.) is comparatively very small. However, these fluids are frequently used in common applications, such as painting, food processing, and many others. Moreover, with a better understanding of the microscopic structure of complex liquids, industries have realized that working fluids can be tailored specifically to optimize existing industrial processes, by altering their formulation (e.g., by means of chemical additives) in such a way as to change one or more physical properties. An example of industrial optimization is the use of polymer additives in agrochemical formulations, which improves the application efficiency of agrochemical sprays and reduces the environmental impact from ground contamination.
This seminar reports some recent investigations of the phenomenology of drop impact for the most common types of non-Newtonian fluids, including power-law fluids, yield- stress (or viscoplastic) fluids, and viscoelastic fluids, both on homo-thermal and on heated surfaces.